Approximately 60% of patients admitted to the intensive care unit for 2009 H1N1 influenza present with acute respiratory distress syndrome (ARDS), which is primarily viral in origin or associated with secondary bacterial pneumonia in about 30% of cases. These patients have a median age of 30 to 45 years, including young children, while fewer than 10% are over 65 years of age. Respiratory distress develops within 4 days, is severe, requires optimal mechanical ventilation, and has necessitated extracorporeal membrane oxygenation (ECMO) in approximately 10% of these patients. Mortality in the ICU is approximately 15%, but rises to 20–25% in cases of ARDS. Early antiviral treatment is associated with survival. (R.A.)